I used GNOME Disks to modify /etc/crypttab and /etc/fstab to auto decrypt and auto mount on boot. Jellyfin still loses its access each time I restart, even though the jellyfin group still displays having access to the files.

Edit: Turns out it does have access, but it’s no longer under the /media/username directory. I have to point Jellyfin to /mnt/UUID instead. This fixed it!

Can I do this with NextCloud or on my phone without killing the battery?

I suppose not. That’s a fair point. Although I will mention, if your camera supports it, location metadata can be embedded automatically. Aves and many other gallery apps support viewing photos with location data on the map.